JP3475353B2 - Variable steering angle ratio steering device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vehicle by a driver.
Suitable steering angle depending on the driving
The steering angle ratio (hereinafter referred to as “steering angle ratio”) of the steered wheels
Variable steering angle ratio steering system that can be dynamically set
You. 2. Description of the Related Art Conventionally, a vehicle is used to assist a driver in driving.
As a steering device, it corresponds to the surrounding environment of the vehicle
One that automatically sets the steering angle ratio is known. Only
In this vehicle steering system, the driver's intention
It was not possible to set the steering angle ratio in accordance with. Accordingly, the present applicant has disclosed in Japanese Patent Application Laid-Open No. 11-789.
No. 44 discloses a variable steering angle ratio steering device for a vehicle
are doing. The variable rudder ratio steering device of this vehicle includes a steering wheel.
Variable steering angle ratio device that can change the amount of rotation of the steered wheels with respect to
To control this variable steering angle ratio device.
It has a control device. Also, variable steering angle ratio device
Is equipped with an electric motor for varying the steering angle ratio. [0004] Then, depending on the vehicle speed, etc.,
Change the amount of steering wheel rotation to
This automatically sets the steering angle ratio. For example,
When traveling lightly on mountain roads where the
Increase the ratio. Conversely, almost on expressways
When traveling at constant speed, make sure that the steering angle ratio is small.
And make sure to set the rudder angle ratio appropriate for each case.
ing. [0005] The prior art disclosed in the above publication
Control unit in the variable steering angle ratio steering system
Circuit (hereinafter referred to as “CPU”),
If a failure occurs in this CPU, the variable steering ratio
The arrangement does not work, causing various inconveniences. like this
In order to avoid inconvenience, for example, two CPUs are provided.
One as the main CPU and the other as the backup CP
U. Normally, the main CPU is used.
Backup CPU in case of failure
Can be used. Such variable steering angle ratio steering
When the backup CPU is used in the device
The main CPU has failed and cannot be used. I
Therefore, to ensure the operability of the vehicle,
In the up CPU, the motor is driven and the steering angle ratio is uniformly determined.
Control to shift the variable steering angle ratio device in the direction in which
Done. Here, the motor is driven to reduce the steering angle ratio.
When trying to move the variable rudder ratio device in the direction
Drive the motive and change to the position where the steering angle ratio becomes the largest
If the steering angle ratio device is located,
For example, it must be moved for about 7 to 10 seconds. this
When the motor is operated for a long time, the motor generates heat,
A drive that supplies current to drive the periphery of the motive or the motor
Field effect transistor (hereinafter referred to as “FET”)
) May be broken. And in this case
Current flows through the FET because the current continues to flow through the FET itself.
The FET generates heat due to the overcurrent, which is caused by the FET.
In some cases, this could lead to disability. When driving the motor, the motor is
The energy efficiency is highest when driving is started. Only
When the motor is driven continuously, the energy in the motor
Unable to effectively use lugi efficient parts
There was a problem. Therefore, an object of the present invention is to provide a variable steering angle ratio steering.
When driving the motor in the device, the motor and FET
Prevents failure of FETs etc. due to heat generation of the body
Another object is to efficiently drive an electric motor. [0009] The present invention has solved the above-mentioned problems.
Akira sought a steering system from the steering wheel to the steered wheels.
Variable steering angle that can change the ratio of the steering angle of the steered wheel to the dollar
And a control device for controlling the variable steering angle ratio device.
Variable steering angle ratio steering device comprising a control device
The variable steering angle ratio device is configured to control the steering with respect to the steering wheel.
An electric motor for varying the ratio of the steered angles of the wheels;
The control device consists of a main CPU that is normally used and a main CPU.
Backup CPU to be used when the CPU fails
And the backup CPU has the
When the in-CPU fails, the motor is driven.
The steering angle of the steered wheels with respect to the operation amount of the steering wheel
The variable steering angle ratio device is shifted in a direction in which the ratio of
Control while driving the electric motor.
Current was supplied to the motor for a predetermined supply time.
After that, the current supply is stopped for a predetermined stop time, and
Supply current for a certain time and stop the current for a predetermined stop time.
Variable steering angle ratio steering device that performs return control
is there. In the present invention, when the main CPU fails,
The backup motor drives the motor
The steering angle of the steered wheels with respect to the steering amount is small.
Control is performed to shift the steering angle ratio device in the following direction. This and
When driving the motor,
After supplying the current for the supply time, supply the current for the predetermined stop time.
Stop and then supply current for a predetermined supply time and stop for a predetermined time
Control to repeat the stop of the current for a time is performed. Therefore,
When the motor temperature rises by supplying current for a predetermined supply time
Even if the motor is stopped for the next predetermined stop time,
Therefore, the electric motor is cooled during the predetermined stop time.
Therefore, it is possible to prevent the motor and its surroundings from becoming hot.
Of the FET due to the heat generated by the motor
Failure can be prevented. In addition, FET itself
Current does not continue to flow,
After the flow, the current does not flow for a predetermined stop time. This
Therefore, it is necessary to cool the FET itself during the predetermined stop time.
To prevent failure of the FET due to heat generation
Can be. In addition, the driving and stopping of the motor are repeated.
Therefore, the motor often starts to drive. Accordingly
The energy-efficient part of the motor
Can be used. In the present invention, the “predetermined supply time” and
And "predetermined stop time" are set to appropriate times
For example, "predetermined supply time" and "predetermined stop
Stop time "can be set to 500ms
You. In addition, "predetermined supply time" and "predetermined stop time"
Do not need to be set to the same length.
"Supply time" is 500ms, "predetermined stop time" is 300ms
Can also be set to Furthermore, "predetermined supply time"
And "predetermined stop time" does not need to be set constant,
For example, "predetermined supply time" and "predetermined stop time"
Set to shift appropriately between 300 and 500 ms
You can also. In addition, the current supply for a predetermined supply time and the predetermined stop
The control to repeat the stop of the current during the stop time is performed by the main CPU.
It can be performed whenever a failure occurs.
Alternatively, the duty ratio of the current supplied to the motor is detected.
And the duty ratio of this current is equal to or greater than a predetermined value, for example,
50% or more of the time is more than a certain time, for example, 50
When the time is 0 ms or more, the current supply is stopped.
After that, control to repeat current supply and stop
Is also good. In addition, this control is controlled by the duty ratio of the current.
An embodiment in which the process is repeated until the value becomes equal to or less than a predetermined value, for example, 50% or less.
It can also be. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to the drawings.
This will be described in detail with reference to planes. First, the present invention
The overall configuration of such a variable steering angle ratio steering device will be described. Figure 1
1 is an overall configuration diagram of a variable steering angle ratio steering device according to the present invention.
The variable steering angle ratio steering device 1 according to the present invention is a steering wheel.
Steering from steering wheel 2 to steered wheels W, W
The variable steering angle ratio device 10 provided in the ring system S and the vehicle speed
A control device 60 for controlling the variable steering angle ratio device 10 based on
Have. In the steering system S, the steering system
The steering shaft 3 provided integrally with the wheel 2
Variable rudder via connecting shaft 4 having universal joints 4A and 4B
It is connected to the input shaft of the angle ratio device 10. Variable steering angle ratio
Is the rotation angle of the output shaft with respect to the rotation angle α of the input shaft.
That can continuously vary the ratio β / α of the degree β
You. A pinion 5 is provided on the output shaft of the variable steering angle ratio device 10.
The pinion 5 and the rack teeth of the rack shaft 6
By engaging the
To the linear motion (L) of the rack shaft 6 and the linear motion of the rack shaft 6
Movement is controlled via the tie rods 7, 7 and the knuckle arm.
The steering wheel W is converted into a steering motion (T). An auxiliary steering wheel is provided beside the rack shaft 6.
Electric power steering device for generating lux
(Hereinafter referred to as “EPS”) motor (hereinafter referred to as “EPS
8) is arranged coaxially with the rack shaft 6.
I have. The rotation of the EPS motor 8 is the same as that of the rack shaft 6.
It is converted to thrust through a ball screw mechanism 9 provided on the shaft.
This thrust is applied to the rack ball screw shaft 9A.
You. Next, one embodiment of the variable steering angle ratio device according to the present invention.
The structure of a body example will be described. FIG. 2 shows the variable steering angle ratio device.
FIG. 3 is an exploded perspective view of a shaft portion of the variable steering angle ratio device,
FIG. 4 is a sectional view taken along line AA of FIG. As shown in FIG. 2, the input shaft 11 is a ball bearing.
Rotatably supported on the upper casing 13a via the bracket 12
Via the ball bearing 15 at the eccentric position of the support member 14
Supported rotatably. Lower case of input shaft 11
At the end protruding into the ring 13b, a rotational force is applied to the output shaft 17.
The coupling 16 for transmitting the force is integrally formed with the input shaft 11.
Have been. The input shaft 11 is connected to the connecting shaft 4 shown in FIG.
Connected and rotate the steering wheel 2
As a result, the input shaft 11 rotates via the connection shaft 4.
It has become. The output shaft 17 has a pair of ball bearings 18.
a, 18b to be rotatable to the lower casing 13b
Supported. The output shaft 17 meshes with the rack shaft 6.
The matched pinions 5 are integrally formed. Lower case
The end of the output shaft 17 protrudes into the ring 13b.
Eccentric from the center of the output shaft 17 at the end of the output shaft 17
An intermediate shaft 19 is protrudingly provided at the closed position. This intermediate shaft 1
9 and a coupling 16 formed integrally with the input shaft 11.
The slider 2 has a flat needle bearing 20 interposed therebetween.
1 and a tapered roller bearing 22
You. Further, between the input shaft 11 and the upper casing 13a.
Is provided with a sealing member 35 having a flexible tubular portion.
Have been. The variable steering angle ratio device is provided by the seal member 35.
The airtightness in 10 is maintained. As shown in FIG.
In the surface, a groove 23 having a trapezoidal cross section which is open at the bottom and open
Are formed. A pair of flat type d
The slider 21 with the idle bearing 20 interposed therebetween
23 are slidably engaged with each other on opposite slopes.
You. A tapered roller is provided at the center of the lower surface of the slider 21.
An intermediate shaft is provided so as to be relatively rotatable via the bearing 22.
19 are engaged. As shown in FIG. 2, the lower casing 13b
Of the ball bearing 18b supporting the lower end of the output shaft 17
The adjustment screw 24 that comes into contact with the lace is screwed
I have. Tightening this adjustment screw 24 appropriately
The pinion 5 is pressed in the axial direction,
Between the input shaft 11 and the output shaft 17 via the
Reload is given. Coupling 1 in this way
6 Removes backlash and improves connection rigidity
You. As shown in FIG. 4, an outer peripheral portion of the support member 14 is provided.
Is partially equipped with a fan-shaped partial worm wheel 25
Have been. This partial worm wheel 25 has a warm
A motor 27 as an electric motor
Driven worm 28 is engaged. And
By rotating the motor 27, the support member 14
Giving rotational movement over a predetermined angular range
Is available. Note that the worm 28 is
Through a backlash removing member 29 using a core cam
It is supported by the upper casing 13a. This buckler
The hexagonal hole 30 formed at the end of the
Engage the hex wrench and attach the hex wrench to the upper
By rotating with respect to the thing 13a, its axis
Moves and the engagement with the partial worm wheel 25 changes.
It is becoming. In addition, the shaft of the worm 28
Worm 28 and worm reducer to allow movement
The structure 26 is connected via an Oldham coupling 31.
ing. The upper casing 13a includes a support member 14
A differential transformer that engages with pins 32 projecting from the upper surface of the
A displacement sensor 33 is attached.
The displacement sensor 33 detects the rotation angle of the support member 14 and
I have. Support member 14 detected by displacement sensor 33
Of the input shaft 11 supported by the support member 14
Of the eccentricity amount signal (actual eccentricity amount) 33a
It is output to the steering angle ratio input circuit 68. The main CPU 61 in the control device 60 (FIG.
7) is the steering angle ratio (target steering angle ratio) set based on the vehicle speed
Detected by the displacement sensor 33 and the target eccentricity corresponding to
With the actual eccentric amount (corresponding to the actual steering angle ratio) 33a
Thus, the operation of the motor 27 is controlled by the feedback control.
It is carried out. Next, the operating principle of the variable steering angle ratio device will be described.
Will be explained. FIG. 5 is a view showing the operation principle of the variable steering angle ratio device.
FIG. 6 is an input / output showing the steering angle ratio characteristics of the variable steering angle ratio device.
It is an angle characteristic figure. As shown in FIG. 5, the rotation center of the input shaft 11 is
A, the center of rotation of the output shaft 17 is B, and the action point of the intermediate shaft 19
Is C. The dimension between BC is b, the input shaft 11 and the output
The amount of eccentricity (dimension between AB) between the shaft 17 and the input shaft
The rotation angle (steering wheel steering angle) of the output shaft 17 is α.
The rotation angle (pinion rotation angle) is β. At this time, since b · sin β = (b · cos β−a) tan α, α = tan ^-1 (B · sin β / (b · cos β-a)). The driver operates the steering wheel 2
When the input shaft 11 is rotated by the
9 is a slider 21 of the coupling 16 of the input shaft 11
, The crank rotates around the axis of the output shaft 17.
You. For example, as shown in FIG.
When the angle α1 is 90 degrees, the rotation angle of the output shaft 17
β1 is as shown in FIG. Here, when the support member 14 is rotated,
3 and 4 by the eccentric cam action of the holding member 14.
The axis of the input shaft 11 changes within the range indicated by reference numerals A0 to A2.
You. Due to a change in the axis of the input shaft 11, the deviation between the input and output shafts is reduced.
The center a is appropriately determined and the axis of the input shaft 11 and the output shaft 17 is determined.
When they are eccentric to each other, the input shaft 11 and the output shaft 17
Are inconsistent with each other. Moreover, the input shaft 11 is equiangular
The angle change of the output shaft 17 when rotating each time gradually increases
(See solid lines a1 and a2 in FIG. 6). The axis of the input shaft 11 and the output shaft 17
Eccentricity a of a2 to a0 (a2>a1> a0 = 0)
When continuously changed in the range, the rotation angle of the input shaft 11
Ratio β / α of the rotation angle of the output shaft 17 to the
The utility steering angle ratio can be continuously changed. I
When the eccentricity a between the input and output axes is increased, the input angle α
The rate of change of the output angle β with respect to
If the amount of eccentricity a is set to 0, it is shown by a dashed line (a0) in FIG.
Thus, the input angle α and the output angle β are equal. The change in the steering angle ratio is determined, for example, in a low-speed running range.
Control to a0 side and to a2 side in high speed driving range
Then, in the low-speed driving range, the steering angle α
Rack stroke set larger than conventional steering system
Thus, more sensitive (quick) characteristics can be realized.
In the high-speed driving range, the steering angle α
The stroke is set smaller than the conventional steering system.
As a result, it is possible to realize a more insensitive (dull) characteristic. But
Therefore, the relationship between the steering wheel angle in practical use and the traveling speed is
Flat characteristics can be obtained. Subsequently, a variable steering angle ratio steering apparatus according to the present invention.
Will be described. As shown in FIG.
In addition, the control device 60 is provided with a main CPU 6 that is normally used.
1 and the main CPU 61 mutually detect a failure.
It has a sub CPU 62, and further has a main CPU
Used when the sub-CPU 61 or the sub CPU 62 fails.
A backup CPU 63. These main CPs
U61, sub CPU62 and backup CPU63
Are connected to the switching circuit 64, respectively. The switching circuit 64 includes the motor driving circuit 6
5 and a switch (not shown)
Motor drive output from the main CPU 61
Output from the backup signal 63 and the motion signal 61a.
Which of the motor drive signals 86a is sent to the motor drive circuit 65
Switching whether to output. The motor drive circuit 65 includes:
Bridge circuit consisting of four FET switching elements
And connected to a battery power source (not shown).
To the motor 27 based on the signal from the switching circuit 64.
The motor 27 is driven by supplying a current. Main CPU 61 and sub CPU 62
Is a gate drive circuit 6 for driving the EPS motor 8
6 to the EPS motor drive circuit 67.
You. The EPS motor drive circuit 67 has a switch of four FETs.
It consists of a bridge circuit consisting of
Not connected to the battery and from the main CPU 61
To the EPS motor 8 based on the EPS drive signal 61b of
The electric motor is supplied to drive the EPS motor 8.
Further, the EPS motor drive circuit 67 and the EPS motor 8
In the meantime, an electric power for detecting a current supplied to the EPS motor 8 is used.
Motive current detection means 71 is provided. This electric motor
Of the EPS motor 8 detected by the
The flow is output to the main CPU 61 and the feedback
Used for control. The control device 60 also includes an actual steering angle ratio input circuit.
A road 68 is provided. The actual steering angle ratio input circuit 68
Of the input shaft 11 (FIG. 2) detected by the position sensor 33.
The displacement amount of the actual steering angle ratio is determined by the main CPU 61 and the sub CPU 6.
2, and output to the backup CPU 63.
You. On the other hand, the control device 60 controls the steering torque input circuit 69A.
And a vehicle speed input circuit 69B. Steering torque input
The force circuit 69A is provided with a torque signal from the steering torque sensor TS.
No. Ta is output to the main CPU 61 and the sub CPU 62.
are doing. The vehicle speed input circuit 69B includes a vehicle speed sensor V
The main CPU 61 and the sub CPU
62 and the backup CPU 63 respectively.
ing. Main CPU 61 in control device 60
Normally controls the variable steering angle ratio device 10
In addition, EPS control is also performed. The sub CPU 62
And with the backup CPU 63
Monitoring is performed to detect failures. Also, sub C
The PU 62 is normally mutually connected with the main CPU 61.
Monitors the main CPU 61 or sub CPU
If a failure is detected at 62, the function is stopped.
You. The backup CPU 63 is a main CPU
Used when a failure occurs in the sub CPU 61 or the sub CPU 62.
Normally, a failure occurs in the main CPU 61.
I am preparing for the control to be performed when I run out. Main CPU6
As a specific control in the event of a failure, the steering angle ratio is
The motor 27 is driven to be small. In this embodiment
In the main CPU 61, the variable steering angle ratio device 10
Not only controls but also controls EPS.
If the main CPU 61 breaks down, the EPS control also stops.
Stop. Driver steers with EPS control stopped
When trying to rotate the ring wheel 2, a large force
I need. At this time, the variable steering angle ratio steering device 10
The smaller the steering angle ratio, the more the steering wheel 2
The force required of the driver when turning is small.
Therefore, when the main CPU 61 breaks down,
The backup CPU 63
The motor 2 so that the steering angle ratio is minimized.
7 is driven. The configuration of the backup CPU 63 will be described.
Referring to FIG. 8, the backup CPU 63
Is a target eccentricity determining unit 81, a deviation calculating unit 82, a PI
D control unit 83, PWM signal generation unit 84, PWM signal
It has a monitoring unit 85 and a gate drive circuit unit 86. The target eccentricity determining unit 81 determines that the steering angle ratio is the minimum.
Table for setting the amount of eccentricity of the variable steering angle ratio device 10
Of the variable steering angle ratio device 10 for obtaining the minimum steering angle ratio.
The eccentricity signal 81a is output. The deviation calculation unit 82
The eccentricity signal 81a is detected by the displacement sensor 33.
The deviation from the actual eccentric amount (corresponding to the actual steering angle ratio) 33a is calculated.
The difference signal 82a is output. The PID control section 83
No. 82a is subjected to processing such as proportionality, integration, and differentiation,
Of the current supplied to the motor 27 to make the difference close to zero.
A drive control signal 83a indicating the direction and the current value is generated and output.
Power. The PWM signal generation unit 84 outputs the drive control signal 83a
For performing PWM operation of the motor 27 based on the
(Pulse width modulation) Generate signal 84a and monitor PWM signal
The output is output to the section 85 and the gate drive circuit section 86. The PWM signal monitoring unit 85 outputs the PWM signal 84
monitoring the duty ratio of the PWM signal 84a.
Based on the duty ratio, a predetermined condition described later is satisfied.
When the gate drive circuit unit 86 receives the prohibition signal 85a
Is output. The gate drive circuit unit 86 outputs the PWM signal 84
The gate of each FET of the motor drive circuit 65 is
Motor for driving and switching driving of each FET
The drive signal 86a is output to the switching circuit 64. Shown in FIG.
If the main CPU 61 or the sub CPU 62 fails,
On the road 64, the signal of the backup CPU 63 is electrically driven.
Is switched to be supplied to the machine drive circuit 65,
Motor drive signal 8 output from gate drive circuit 86
6a is supplied to the motor drive circuit 65 via the switching circuit 64
Is done. Then, the gate drive circuit unit 86 outputs the PWM signal
The gates of each FET of the motor drive circuit 65 are
To drive each FET for switching. Subsequently, the variable steering angle ratio steering according to the present embodiment is described.
FIG. 4 is a diagram showing control of the variable steering angle ratio device 10 in the device 1.
7 and FIG. In the control device 60,
Main CPU 61, sub CPU 62, backup CP
Individual processing is performed in each of U63.
These processes will be described specifically.
In U61, during normal traveling, the vehicle speed sensor VS
Of the variable steering angle ratio device 10 based on the vehicle speed signal Va from the
The target steering angle ratio is set. Also, the output from the displacement sensor 33 is
The applied eccentricity signal (actual eccentricity) 33a and the target steering angle ratio
The drive amount of the motor 27 is calculated by comparison. This motor
Motor to supply a current corresponding to the drive amount of
Generates drive signal 61a and switches motor drive signal 61a
The signal is output to the circuit 64. Normally, the switching circuit 64
The motor drive signal 61a from the main CPU 61.
Is output to the motor drive circuit 65. Motor drive circuit 6
5, the electric motor output through the switching circuit 64
The motor 27 is driven based on the drive signal 61a,
The steering angle ratio of the steering angle ratio device 10 is set. Drive of motor 27
When the steering angle ratio is set by the movement, the variable steering angle ratio device 10
The amount of eccentricity is detected by the displacement sensor 33. Displacement sensor 33
The eccentricity amount signal 33a detected by the control is input to the actual steering angle ratio input.
Output from the actual steering angle ratio input circuit 68 to the main
Output to the CPU 61 and used for feedback control.
You. The main CPU 61 has a sub CPU 6
2 and the main CPU 61
Or when a failure is detected in any of the sub CPUs 62
Has the functions of the main CPU 61 and the sub CPU 62.
Stop. Main CPU 61 and sub CPU 62
When the function stops, the main CPU 61 and the sub CPU 6
Status signals 61b and 62 input from the second to the switching circuit 64
b (normal 1; fault 0) becomes 0. In the switching circuit 64, the main CPU 6
1 and the status signal output from the sub CPU 62 becomes 0
The main CPU 61 or the sub CPU
62 failures are detected. Main CPU 61 or sub C
When the failure of the PU 62 is detected, the switching circuit 64 operates.
The motor drive signal 86 from the backup CPU 63
a is output to the motor drive circuit 65 via the switching circuit 64.
Will be able to In the backup CPU 63, the main CP
Whether a failure has occurred in U61 or sub CPU62
Regardless, the same processing is performed. This backup
The processing in the CPU 63 will be described.
In the CPU 63, the target eccentricity setting unit 81
The variable steering angle ratio in the steering angle ratio device 10 is minimized.
Is set to the target eccentricity. Target eccentricity setting unit 81
Outputs the target eccentricity amount signal 81a to the deviation calculating section 82.
Have been. Also, the variable steering angle detected by the displacement sensor 33
The amount of eccentricity of the ratio device 10 is detected by the displacement sensor 33.
Eccentricity amount signal 33a from displacement sensor 33 is actually steered.
It is output to the angle ratio input circuit 68. Eccentricity signal 33a
Is connected to the backup CP via the actual steering angle ratio input circuit 68.
It is output to the deviation calculator 82 in U63. Deviation calculation
The unit 82 includes a target eccentricity amount signal 81a and an eccentricity amount signal 33a.
And the deviation signal 82a is sent to the PID control unit 83.
Output. The PID control unit 83 responds to the deviation signal 82a
Process such as proportional, integral, and derivative to reduce the deviation to zero.
Of the current supplied to the motor 27 and the current value
And a drive control signal 83a indicating
84. The PWM signal generation unit 84 outputs the drive control signal.
No. 83a for performing the PWM operation of the motor 27
A PWM signal 84a is generated. This PWM signal 84a is
Output to PWM signal monitor 85 and gate drive circuit 86
Power. The PWM signal monitor 85 generates a PWM signal.
Based on the PWM signal 84a output from the unit 84,
Is output to the motor drive circuit 65.
Sometimes, the electric power is supplied from the motor drive circuit 65 to the motor 27.
The current direction and current value. Specifically, P
While detecting the duty ratio of the WM signal 84a,
The time during which the WM signal 84a is being input is measured. Soshi
From the duty ratio of the PWM signal 84a, the motor 27
The current value to be supplied to the power supply is detected. As a result, even if
For example, the time when the duty ratio is 50% or more is 500
ms, the gate drive circuit unit 86
Output the prohibition signal 85a for, for example, 500 ms.
You. Then, after starting to output the prohibition signal 85a, 500
After the elapse of ms, the output of the inhibition signal 85a is stopped.
If the output of the inhibition signal starts to be inhibited, the PWM signal 84
Measurement of the time when the duty ratio of a is 50% or more
To start. Then, the duty ratio of the PWM signal 84a
Is more than 50% for more than 500ms
At this point, the output of the prohibition signal 85a is started. Hereafter, the same
Repeat the process. The gate drive circuit 86 generates a PWM signal.
Based on the PWM signal 84a output from the unit 84,
The gate of each FET of the motivation drive circuit 65 is switched
A motor drive signal 86a for operating the motor is generated. This and
The prohibition signal 85a is output from the PWM signal monitoring unit 85.
If not, the motor drive signal 86a is switched to the switching circuit 6
4 is output. On the other hand, the prohibition signal from the PWM signal monitoring unit 85
No. 85a is output, the motor drive signal 86
The output of a is stopped. Thus, the backup CPU 63
Output the motor drive signal 86a to the switching circuit 64.
Have been. In the switching circuit 64, the main CPU is normally used.
A motor drive signal 61a from the motor drive circuit 65
Output from the backup CPU 63.
Motor drive signal 86a is output to motor drive circuit 65
It will not be done. In contrast, the main CPU 61
If a failure occurs in the sub CPU 62,
Output from the gate drive circuit unit 86 of the CPU 63
The motor drive signal 86a is output to the motor drive circuit 65.
You. In the motor drive circuit 65,
Based on the motor drive signal 86a output
The steering angle is driven in the direction in which the steering angle ratio decreases.
The ratio device 10 is shifted. Here, the prohibition signal from the PWM signal monitoring unit 85 is output.
No. 85a is output to the gate drive circuit unit 86
, The motor 27 is not driven. PW
The reason that the M signal monitoring unit 85 outputs the inhibition signal 85a is the P signal
The duty ratio of the WM signal 84a is 50% or more
When the time exceeds 500 ms, in other words,
Current is supplied to the motor 27 so that the motor 27
It's time to start. Here, the prohibition signal 85a is PWM
Output from the signal monitoring unit 85 to the gate drive circuit unit 86,
As a result, the supply of current to the motor 27 is stopped.
The motor 27 stops. When the motor 27 stops
Therefore, the motor 27 that has started to have a large heat is cooled,
FE in the motor drive circuit 65 due to the heat of the motor 27
The failure of T can be prevented. And the FET itself
Current does not continue to flow, but during the predetermined supply time,
After the current flows, the current does not flow for a predetermined stop time.
Therefore, the FET itself is cooled during the predetermined stop time.
To prevent FET failure due to heat generation.
Can be. Further, the variable steering angle ratio device 10 is quickly shifted.
Signal 85a was output for 500 ms
At this point, the output of the prohibition signal 85a is stopped. Prohibition signal 8
When the output of 5a is stopped, the motor 27 starts driving again.
In order to reduce the variable steering angle ratio, the variable steering angle ratio device 10
Start migrating. And a motor having a predetermined current value.
If the drive time of the 27 exceeds 500 ms, in other words,
A PWM signal 84a having a duty value of 50% or more is output.
If the time exceeds 500 ms, the PWM signal monitoring unit 85
Outputs a prohibition signal 85a to the gate drive circuit 86.
You. As a result, the motor drive signal to the motor drive circuit 65
The output of 86a is stopped, and the motor 27 stops. Less than
Thereafter, by repeating this procedure, the motor 27
Supply and stop of current can be repeated. in this way
Then, the driving and stopping of the motor 27 are repeated.
27 starts to drive more often. Therefore,
Effective use of energy-efficient parts of
can do. In this way, the PWM signal monitor 85
Output the prohibition signal 85a or output the prohibition signal 85a
By stopping the motor, supply of electric current to the motor 27 is performed.
Control to repeat feeding and stopping can be performed. The preferred embodiment of the present invention has been described above.
As described above, the present invention is not limited to the above embodiment.
Absent. For example, repeatedly supplying and stopping the current to the motor
Although the PWM duty ratio is used for control,
Current detected by the current detection means, and
Control to stop the current supply when the current of
It can be carried out. Also, a signal from the displacement sensor 33a
The speed of the motor 27 is calculated based on
When the degree is equal to or more than the predetermined value, the prohibition signal 85a must be output.
May be added. Further, in the above embodiment,
Performs EPS control as well as variable steering angle ratio control.
However, only the control of the variable steering angle ratio device is performed.
You can also. As described above, according to the present invention, the electric motor
And its surroundings can be prevented from becoming hot
As a result, the FET caused by the heat generated by the motor and the FET itself
Obstacles can be prevented. Also in motors
Effective use of energy-efficient parts
Becomes

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an overall configuration diagram of a variable steering angle ratio steering device according to the present embodiment. FIG. 2 is a front sectional view of the variable steering angle ratio device according to the embodiment. FIG. 3 is an exploded perspective view of a shaft portion of the variable steering angle ratio device according to the present embodiment. FIG. 4 is a sectional view taken along line AA of FIG. 2; FIG. 5 is an explanatory diagram illustrating an operation principle of the variable steering angle ratio steering device according to the present embodiment. FIG. 6 is an input / output angle characteristic diagram showing a steering angle ratio characteristic of the variable steering angle ratio steering device according to the present embodiment. FIG. 7 is a block diagram of a control device of the variable steering angle ratio steering device according to the present embodiment. FIG. 8 is a block diagram showing a configuration around a backup CPU according to the embodiment; [Description of Signs] 1 Variable steering angle ratio steering device 2 Steering wheel (handle) 10 Variable steering angle ratio device 27 Motor (electric motor) 33 Displacement sensor 60 Control device 61 Main CPU 62 Sub CPU 63 Backup CPU 64 Switching circuit unit 65 Electric motor Drive circuit unit 84 PWM signal generation unit 85 PWM signal monitoring unit S Steering system W Steered wheels

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-11-78943 (JP, A) JP-A-2000-62632 (JP, A) JP-A-11-78944 (JP, A) JP-A-6-298105 (JP, A) JP-A-2-258472 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B62D 6/00 B62D 5/04

Claims (1)

(57) [Claim 1] A variable steering angle ratio device capable of changing a ratio of a steering angle of a steering wheel to a steering wheel is provided in a steering system from a steering wheel to a steering wheel, and the variable steering angle is provided. A variable steering angle ratio steering device including a control device for controlling a ratio device, wherein the variable steering angle ratio device includes an electric motor for varying a steering angle ratio of the steered wheels to the steering wheel; The device has a main CPU used at normal time and a backup CPU used when the main CPU fails. The backup CPU drives the electric motor when the main CPU fails. Controlling the shift of the variable steering angle ratio device in a direction in which the ratio of the steering angle of the steered wheels to the operation amount of the steering wheel decreases, and driving the electric motor. In this case, after supplying a current for a predetermined supply time to the electric motor, the supply of the current for a predetermined stop time is stopped, and thereafter, a control for repeatedly supplying the current for a predetermined supply time and stopping the current for a predetermined stop time is performed. A variable steering angle ratio steering device, comprising: